Furnace for melting metals.



E. BOSSHARDT.

FURNACE ron MELTING METALS.

APPLICATION FILED DEC.28, 1914 Patented Dec. 21, 1915.

v2 SHEETS-SHEET I.

ifzizesse E. BOSSHARDT.

FURNACE FOR MELTING METALS.

APPLICATION FILED DEC. 28, 1914. I 1,164,983. Patented Dec. 21, 1915.

2 SHEETS-SHEET 2.

il i'nessea: Invezzfor:

. of the furnace into the ,meltingroom, where I EDWIN BOSSI-IAR'DT, OF EMMENBIR-fi'CKE, NEAR LUCERN'E, SWITZERLAND.

runNAcE non MELTING METALS.

Specification of Letters Patent.

Patented Dec. 21, 1915.

- Application filed December 28, 1914. Serial No. 879,335.

to the accompanying drawings, and .to letters or figures of reference marked thereon, which form a part of this specification.

The known open hearth furnaces are of the reverberatory type and they have a gas firing and gas and air chambers arranged beneath the furnace. 'These chambersact aspreheating chambers and the gas andair. stream from these chambers through fiues,

provided inthe furnace-heads or ends into the melting-room, where they mix and Where they are burned up. -It has also been proposed to provide, near eachf end of such reverberatory furnace, agas-generator and to guidethe gas produced in these generators and the preheated air through the end'walls they can mixand where they are. burned up. lnlthesevtwokinds of open hearth furnaces the gas and theair stream through.

slotsprovided in the head or end walls into the melting room. "These slotsare disposed in ,sucha manner that the gas streams mto.

the melting room near its middle and the air near its two ends, or the gas streams 1n.

near the lower level and the air near the upper, le'velof said room. However, in both instances a' good and quick mixing of the gas and air does not take place and the gas is not wholly burned up, so that it may come into contact with the furnace charge. For this reason it was not possible to attain in the hitherto open hearth Ifurnaces a sufiicient high melting temperature.

In the production of very tOUgh tmStdIOD, particularly of cast steel used for casting pieces having very thin walls, for instance walls of only .two millimeters thickness, it

has been found, that the material obtained in the hitherto known open hearth'furnaces is not adapted for casting thin pieces. If

the metalproduced in such furnaces is used for casting pieces of large size the formation of shrinking holes, or so called pipes, can-J v not be prevented and upon a cooling of such cast pieces cracks will appear at the places where the thinyandthick walls are joined. This proves, that the casting material-has not been sufliciently tough and liquid. These drawbacks are in consequence of the insuflieient mixing of the gas and air and of the I too low melting temperature resulting there.-

from.

Hitherto the casting of very thin and complicated pieces could only be effected, in a satisfactory manner, by using crucible cast steel, the latter being more suitable for this purpose than the metal obtained by proceeding according tothe different refining processes. It is, however, well known thatthe process for producing crucible cast-steel is more expensive than the refining processes, (Bessemer, Thomas, or hearth refining proce'sses).-

It has, therefore, been proposed to improve the hearth refining process, which, with the exception of the process forproducing crucibles, gives the purest material by raising the heat in the furnace in some 'way or otherto a-higher degree, in order to factory, asan admixture of oil has the effect of accelerating the crumbling of the brickwork, so that the whole process becomes very unremunerative. v v v f The object/of the present invention is to provide a hearth-furnace of the Siemens- Martin or open hearth furnace type in which all the hereinbefore mentioned drawbacks.

are eliminated. The main feature of the hearth furnace constructed according to my invention and provided 1n a known manner with gas-generators arranged adjacentto each furnace head or end and with gas outlet-openings arranged below the outlet openings 'for the preheated air, consists in the provision in each end wall of the furnace of at least one horizontal slot arranged below said gas outlet-openings and on the level of the white heat zone of the gas-generators and connecting the generators with the melting room of the furnace.

A further importantfeature of my invention consists in the provision of at least one channel in each furnace head adapted to preheat the gas produced in the generators be.-. fore 1t streams 1n'to the melting room. In such a hearth furnace the gasstreanung into the melting room comes tolie between the broad layers of heated air flowing into said room and the flames streaming from the white heat zone of the coal firing into the melting room. In this manner the gas stream will be surrounded by said air layers and said flames, so that it will be wholly burned up; The result of this is, that the temperature in the melting room will rise to a very high degree and that a very pure andtough melting product is obtained.

One mode of carrying the invention into effect is shown by way of examplein the accompanying drawings, in which:

Figure 1 is avertical longitudinal section through the furnace, Fig. '2 is a planview of the. furnace showing partly a section on the line AB of Fig. 1. Fig. 3 is a section on the line C D of Fig. 1, and Fig. 1 is a section on the line EF of Fig. 1.

i In the embodiment of the invention shown in the drawings, 1v denotes the hearth or melting room, and 2 the two head ends of the furnace. The generators 3 are arranged ad acent these heads 2 and the grates & of-

the generators are charged by means of the loading hoppers Beneath the grates -.t there are arranged in a known manner the air distributers Gsupplied with CUII'IPI'QSSECI air through the pipes 7,'by ablower not shown in the drawings.

8 denotes air chambers arranged beneath.

the hearth 1 and adapted to preheat the air. For this purpose they are built as regenerators acting in the samemanner as the regenerators of'the known open hearth or Siemens-Martin furnaces. Channels 9 connect these chambers S to the furnace-heads 2, the ends of these channels being arranged in the upper part of the heads 2 forming vaulted and downwardly directed slots 9,

so that the hot air streams in at the uppermost level of the melting room 1. The chambers 8 are also connected by means of. channels 10 to a chamber 12 provided with a butterfly valve 11. .A channel 13 connects the chamber 12 with the chimney and a channel-H connects said chamber with the atmosphere (Fig. 2).

Channels 15 provided in the furmice-heznls 2 connect the upper end of each gas generator 3 with regulating boxes 16 provided with valves 17 adapted to close the openings communicating with the horizontal preheating channels 18. In each furnace head 2 there is provided such a channel 18. The outlet' openings 19 of these channels lo. through which the gas produced in'the generators streams into the hearth room 1. are arranged beneath the slots 9. Pipes 21) connect the regulating boxes 16 of one head of the. furnace with the boxes, of the head on levers and a hand lever 23 provided on this rod, (Figs. 1, 3, and 4). Between each gas generator and the melting room 1 there is provided on the level of the white heat zone of the generators a horizontal slot 2% arranged beneath the two corresponding gas out-let openings19.

25. denotes working openings and 26 the trough communicating with the tap-hole.

The process of melting a metal, for instance, cast-steel, in the 'hereinbefore described furnace may be carried out as follows: The butterfly valve 11 is alternately reversed in sucha manner that at one time the fresh air streaming through the channel 1+ passes through the chaniiel 10 disposed on one side of the furnace. the corresponding chamber 8, the corresponding channels 9 and the slot 9 into the melting room 1, where it last mentioned chamber 8 heat thereby the ret'ractory bricks, which are so arranged thatthey inclose a. number of holes between them (not shown in'the drawing). Thus, these bricks will become red 'hot.- At an-j other time the air streams in a reversed direction through the furnace, whereby it is heated while streaming. through thelast mentioned chamber 8 and. the gasesleaving the furnace heat the other chamber 8.

so that, when the freshair streams at first again through this chamber '8, it will be heated. From the foregoing it is evident, that the air streaming into the hearth room 1 is always preheated.

The two gas generators 3 are 'simultane ously started. The gas produced in these generators streams through "the channels 15 into the regulating boxes 16. Upon a re- \ersal of the air supply from one side of I the furnace to the other side the gas supply has also to be reversed. 1'. 0., one of the generators 3 has to be connected directlv with the hearth. while the gas supplv from the other generator to the hearth has to be interrupted. 'lo this end I correspondinglv open alternately the gas passage connectinii the boxes 16 with the gas preheating chan-;

nel l8 and the openings 19 of the furnace side on which'the preheated air passes erator on this side through the corresponding channel 18 and the openings 19 into the hearth or melting room 1, and since the channels 18 preheat this gas, it will be heated to a high degree when it streams into said room.

The generators are filled with coal, and

heat flows continually from the white-glowing coal through. the slots 24 from below into the melting room 1. fresh air streams into the room 1 near the uppermost level and the flames produced in the white-glowing coal zone streams in near the lowerlevel of said room, while the preheated gas passing through the head ofthe furnace streams in-near thev middle of the melting room 1. -In this manner the gas is wholly inclosed by the superheated air and the thin flames of the white-glowing coal zone. Thus, a very good mixture of gas and air is obtained,' which is immediately ignited, the. gas being thereby completely consumed. The result of this 1s,

that the temperature in the furnace will rise to 2000 C. and more. Owing to this very high melting temperature an absolutely pure and tough material is obtained; in other words, the steel produced is very poor in carbon, so that it is very tough. In the hereinbefore described hearth furnace, .the

gas never comes in a pure unmixed condition into contact with the furnace charge.

Such a furnace .may, therefore, also beused for producing mild'steel or ingot-iron and weld iron. In this latter case the generators 3 are not quite filled with carbon, so that apart of the fire gases streams directly through the slots 24 into the hearth room 1. The hereinbefore described open hearth furnace may, however, as well be used for melting malleable iron, cast iron, and bronze.

In a hearth furnace of the hereinbefore described type mild steel and cast steel may be produced as well by proceeding according to the acid process as by proceeding according to the basic process.

While the starting of an open hearth or Siemens-Martin furnace of the known open type requires 10 to 14 daysfthe temperature at which the charge may be introduced be-.

ing attained only after this time, the furnace .according to this invention may be made ready in about three days for receiving the first charge. Owing to the fact, that a small charge of 1000 to 1500 kilograms 1s introduced, the material may be heated to a The superheated higher degree than is the case, if a great charge is introduced, so that it becomes very liquid. The result of this is, that the molten metal can be poured very. quickly into the molds so that even very complicated castings having walls of only three millimeters I thickness can be very well cast, This is not possible if the metal is melted in a furnace of a greater size. Into a furnace of the hereinbefore described type there may be introduced and melted at least four charges during twenty-four hours. l

The advantages obtained by providing the hereinbefore mentioned slots 24 may be best deduced from the fact, that in a furnace adapted to receive a charge of 1000 to 1500 kilograms the heat streaming from the white-glowing coal of the generators 3 into the melting room 1 raises the temperature in thelatter to about 1600 C.' 4

As I have already'stated, the channels 18 provided in the heads of the furnace and.

a melting room, in combination with gasgenerators arranged adjacent each furnace head, air regenerators, a1r-passages connectmg each of said regenerators with the melttppen hearth furnaces (Siemensing room, at the hearth level means forming a direct communication between the white heat zone of the generators and the melting room and means to guide the gas produced in the generators into the melting room.

3. An open hearth furnace consisting of a melting room, in combination with gasgenerators arranged adjacent each furnace head, air-regenerators, air-passages in the furnace-heads and connecting each of said regenerators with the melting room, a passage in each furnace-head forming a direct communication betweenthe white heat zone of the generators and the melting room and channels adapted to guide the gas produced in the gas-generators into the melting room, the outlet openings of these channels being arranged below the outlet openings of the head, air-regenerators, air'passages in the furnace heads and connecting each of said regenerators with the melting room, a horizontal slot in each furnace head arranged generators arranged adjacent each furnace I on the level of the white heat zone ofthe generators and' adapted to put this zone into communication with the melting room,

and channels adapted to guide the gas produced in the gas-generators into the melting room, the outlet openings of these channelsibeing arranged below the outlet openings of the air passages and abovesaid horizontal slots.

5. An open hearth furnace, consisting of a melting room, in combination With gasgenerators arranged adjacent each furnace head, air regenerators, air passages in the furnace heads and connecting each of sald into the melting room.

6. An open hearth furnace, consisting of a melting room, in combination with gasgenerators arrangediad acent each furnace head, air-regenerators, air passages in the furnace heads and connecting each of said regenerators with the melting room, a-ho-rizontal slot in each furnace head arranged.

on the level of the white heat zone of the generators and adapted to put this zone .into communication with the melting room, gas-channels in each furnace head communicating with the gas-generators, and a horizontal gas preheating channel in each fur- 1,1e4,ess

nace head connected, with said gas channels and having several passages communicating with the melting room, these passages being arranged below the outlet, openings of the air passages and above said horizontal slots.

7. An open hearth furnace, consisting of a melting room, in combination with gasgenerators arranged adjacent each furnace head, air regenerators, air passages in the furnace heads and connecting each of said J regenerators with the melting room, a horizontal slot in each furnace head arranged ,on'the level of the white heat zone of the generators and adapted to put: this zone into communication with the melting, room, gas channels in each furnace head communicating with the gas generators, a horizontal gas preheating channelin each furnace head connected With said gas channels and having several passages communicati'ng with the melting room, these passages being arranged below the outlet vopenings of the air passages and above said horizontal slots, and means adapted to control the connection between the gas channels and the preheating channel of each furnace head;

8. An open hearth furnace comprising a melting chamber, a gas generator chamber adjacent the latter and a direct straight passage way connecting the'white heat zone of the generator and melting chamber for the purpose of supplying radiant heat of said zone tothe melting chamber.

In testimony that I claim the foregoing as my invention, I have signed my name in presenceof two subscribing witnesses.

- j. EDWIN BOSSHARDT.

Witnesses:

CHARLES FISCHER, J osnr SONNANI. 

